Family names on door walls

Door entry seen in Brussels: Names

As the communication system is destroyed, people write their name directly on the wall... and one can see how names are updated over time. It's then possible to read the "history" of the building by looking at who lived there (and make assumptions based on the ethnicity of names). I would be curious to know (and see) who shade the previous names. What does that mean for urban computing?

(I removed the building number on the street, and some other information to avoid finding where this is located).